A tropical storm hit central Vietnam on Monday, threatening severe floods, landslides and substantial damage to coffee output from the world's second-largest producer of the crop.

Tropical Storm Noul, with winds of 88 kph (55 mph), made landfall around the beach resort of Nha Trang late on Monday and weakened to a tropical depression, state radio said.

Noul is expected to cross the coffee-growing province of Lam Dong during the peak of the harvest in the Central Highlands. Torrential rains could halt the harvest and prevent farmers from drying beans outdoors, causing delays and lowering quality.

"There will be heavy rains that will cause flooding and landslides over the next two days," Bui Minh Tang, director of the national weather forecaster, told the Voice of Vietnam.

Heavy rains were still expected in the densely populated Mekong Delta, which normally avoids the worst of the storms that roll in from the South China Sea.

All offshore oil production from Vietnam, Southeast Asia's third-largest producer of crude oil, remained operational, a PetroVietnam official said.

However, state television said Vietsovpetro, a Russian joint venture, would temporarily shut operation on four oil rigs and evacuate workers.

Deputy prime minister Nguyen Sinh Hung had ordered the immediate recall of all fishing boats in the area and said children should not go to school as preparations were made for mass evacuations across a 400 kilometres (250 mile) swathe of coastline.

More than 74,000 people needed evacuation while more than 133,000 fishermen were urged to take shelter, the government said.

In neighbouring Cambodia, prime minister Hun Sen canceled a scheduled trip on Tuesday to the coastal province of Kampot, abutting Vietnam, because of the storm.

Vietnamese government reports said more than 17,000 fishing boats were operating near the Spratlys in the path of the storm.

The Mekong Delta, where the latest rice crop has been harvested, is rarely hit by storms. Typhoon Linda caught the region unawares in November 1997, killing at least 464 people.

The government never revised an initial tally that listed more than 3,200 people as missing.